Parturition Flashcards
What are the three stages of labor?
1) dilation of the cervix
2) expulsion of the fetus
3) expulsion if the placenta
Parturition?
Expulsion of the fetus and placenta from the uterus
What labor stage is the longest?
Stage one: dilation of the cervix
What are the 2 requirements for the expulsion of the fetus?
Myometrium contractions, dilation of the cervix
What hormones stimulate the myometrium contractions?
PGF-2a: contractions of myometrium and luteal regression
Oxytocin: myometrial cintractions itself and stimulates PGF production
Which hormones stimulate the dilation of the cervix?
Relaxin
PGF-2a
What three things occur in the stage of dilation of the cervix?
1) loss of collagen
2) loosening or separation of collagen fibers
3) stage of labor that takes the longest ad also associated with distocia
What two things comprise the endocrinology of parturition?
1) removal of the progesterone block
2) estrogen to progesterone ratio
What steps must take place for the progesterone block to be removed?
P4 blocks E2 receptor and oxytocin receptor formation and PGF synthesis. Removal of P4 permits receptor formation and PGF synthesis
A __ estrogen:progesterone ratio promotes myometrial excitability (contractions).
High
Ferguson reflex?
A neuroendocrine reflex in which the head of the fetus presses on cervix stimulating release of oxytocin from posterior pituitary gland
What is the ferguson reflex facilitated by?
A high E:P ratio
What is the function of oxytocin in the ferguson reflex?
Stimulate myometrial contractions and PGF release from uterus
Oxytocin receptors ___ 40-100 fold at term in women.
Increase
Oxytocin concentrations change little during ___ but increase greatly during ___.
Initial stages of labor
Expulsion of the fetus
In the ewe, what is parturition initiated by?
The fetus
How does the fetus stimulate parturition in the ewe?
1) maturation of the fetal hypothalamus.
2) fetal corticotropin releasing hormone (CRH) stimulates anterior pituitary to release adrenocorticotropic hormone (ACTH)
3) ACTH stimulates fetal adrenal gland to release cortisol
4) fetal cortisol induces placental production of enzymes that metabolize P4 to E2
5) increased E2 and cortisol stimulate increased PGF production by uterus
What 2 things remove the P4 block?
1) CL regression (PGF)
2) placental conversion of P4 to E2
Which hormone increases elasticity of cervix and birth canal? Where is it found and stimulated by?
Relaxin: from CL or placenta; stimulated by PGF
What 4 factors cause myometrial contractions?
E:P
Ferguson Reflex
Oxytocin
PGF
In women, which hormone does not decline at parturition?
P4
What are the two earliest identifiable events of parturition?
Increase PGF
Increase oxytocin receptor
Which hormone increases cervical, vaginal secretions-lubrication?
Estrogen
Water breaks?
Head and feet of fetus push on amnion/allantois rupturing membranes-lubrication
Fetal hypoxia?
Fetus deprived of oxygen in birth canal - stimulates uterine contractions
Uterine contractions are accompanied by ___ contractions.
Abdominal
What is one way pressure is reduced in parturition?
By the release of chorionic villi facilitated by vasoconstriction of villi arterioles
Hemochorial placenta?
Maternal vasoconstriction reduces hemorrhaging
Three reasons for distocia?
1) large fetus
2) abnormal presentation of the fetus (breach), abnormal limb presentation
3) multiple birth
Skunk cabbage?
Sheep had prolonged gestation and congenital hypoplasia of anterior pituitary gland
Gene defects?
Recessive gene in Holsteins had prolonged gestation due to pituitary hypoplasia
How can parturition be induced in cattle and sheep?
By injecting corticosteroids
What 6 things do hormonal changes cause?
1) final maturation of fetus
2) expansion of birth canal
3) maternal behavior
4) synthesis and ejection of milk
5) initiation of uterine contractions
6) termination of pregnancy
Which hormone completes final mammary development and milk secretion?
Prolactin
Fescue toxicity problems?
Ergot causes inhibition of prolactin release and thus milk production
Which hormone stimulates lung surfactant?
Cortisol
Which hormone initiates parturition and lung development?
Fetal cortisol
